--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+include "basic_2/rt_computation/cpms_aaa.ma".
+include "basic_2/dynamic/cnv.ma".
+
+(* CONTEXT_SENSITIVE NATIVE VALIDITY FOR TERMS ******************************)
+
+(* Forward lemmas on atomic arity assignment for terms **********************)
+
+(* Basic_2A1: uses: snv_fwd_aaa *)
+lemma cnv_fwd_aaa (a) (h): ∀G,L,T. ⦃G, L⦄ ⊢ T ![a, h] → ∃A. ⦃G, L⦄ ⊢ T ⁝ A.
+#a #h #G #L #T #H elim H -G -L -T
+[ /2 width=2 by aaa_sort, ex_intro/
+| #I #G #L #V #_ * /3 width=2 by aaa_zero, ex_intro/
+| #I #G #L #K #_ * /3 width=2 by aaa_lref, ex_intro/
+| #p * #G #L #V #T #_ #_ * #B #HV * #A #HA
+ /3 width=2 by aaa_abbr, aaa_abst, ex_intro/
+| #n #p #G #L #V #W #T0 #U0 #_ #_ #_ #HVW #HTU0 * #B #HV * #X #HT
+ lapply (cpms_aaa_conf … HV … HVW) -HVW #H1W
+ lapply (cpms_aaa_conf … HT … HTU0) -HTU0 #H
+ elim (aaa_inv_abst … H) -H #B0 #A #H2W #HU #H destruct
+ lapply (aaa_mono … H2W … H1W) -W #H destruct
+ /3 width=4 by aaa_appl, ex_intro/
+| #G #L #U #T #U0 #_ #_ #HU0 #HTU0 * #B #HU * #A #HT
+ lapply (cpms_aaa_conf … HU … HU0) -HU0 #HU0
+ lapply (cpms_aaa_conf … HT … HTU0) -HTU0 #H
+ lapply (aaa_mono … H … HU0) -U0 #H destruct
+ /3 width=3 by aaa_cast, ex_intro/
+]
+qed-.